# Inquiry about suitability of using an Arduino sensor for my project

I would appreciate any helpful information any of you might be willing to provide.

I am building a water powered motor (WPM) that will be used to power an alternator.

The speed of the alternator is critical. As is known, the RPM rate of the alternator's drive shaft determines the voltage, amperage, and the frequency output of the alternator.

Since I want the alternator to produce 120 VAC @ 60 Hz, the alternator's drive shaft must maintain 3600 RPM, regardless of the load place on the alternator's output, to maintain that voltage and frequency.

As is also known, the larger the load amperage that is placed on the alternator's output, the greater will be the rotational torque, required on the alternator's shaft, to maintain the needed RPMs, which the WPM will need to supply for any given or varying load.

The WPM's rotational torque on its shaft is provided by a rotating drum that has water being pumped into it and then exits the drum through jetted ports placed along the outer surface of the drum.

The force of the water exiting those jets is determined by the pressure of the water being pumped into the drum and also the centrifugal force of the water inside the drum created by the drum's rotation; which in turn determines the WPM's shaft speed and resulting rotational torque.

Under a varying load on the Alternator's output:

(a) If the load increases, there will be a corresponding increase of "breaking pressure" placed on the Alternator's shaft which if left unchecked would slow down it's rotational speed and thus lower its output voltage, etc., if the WPM's output remains the same. Thus to maintain the Alternator's necessary speed, the WPM's power output needs to be increased accordingly by increasing the water flow pressure into its drum.

(b) Conversely, if that load decreases, the Alternator's "breaking pressure" will be reduced, causing an increase in the Alternator's rotational speed, thus increasing its output voltage, etc. above that which is desired. Thus the water supply to the WPM needs to be decreased to maintain the Alternator's optimal RPMs.

I would like to use a proportional water valve to control the water flow rate into the drum as needed.

I would like to control the amount of volume through the proportional valve by monitoring the voltage output of the Alternator.

If that voltage rises above 120 VAC, I want to be able to begin closing the valve until the Alternator's voltage returns to 120 VAC.

Likewise, if the Alternator's voltage falls below 120 VAC, I want the valve to begin opening wider until that proper voltage is restored.

My question: Is the above something that can relatively easily be accomplished by an Arduino sensor and program?

If so, what type of Arduino sensor do I need to use?

I realize that this is the wrong forum to seek help in writing the needed Arduino code, so all I am seeking is information on the possible suitability of using an Arduino sensor to provide my desired valve controller.

yes, an arduino can do this.

to measure RPM, you need to put something on the shaft.
if there is a section that is in free air, then a reflective dot and a IR sensor can work.
look up arduino tachometer.

to control the damper, you need to get that damper motor and then control that. this too is something that should have a lot of hits on a google search.

rickinva:
Since I want the alternator to produce 120 VAC @ 60 Hz, the alternator's drive shaft must maintain 3600 RPM, regardless of the load place on the alternator's output, to maintain that voltage and frequency.

I suspect it would be a great deal easier to generate at whatever speed the alternator chooses to work at and use electronics to produce the correct voltage and frequency. For example that is what Honda does with their small petrol generators.

If you rectify the alternator output to DC then you can use an off-the-shelf inverter to produce the the AC output. That's how this laptop is being powered as I type.

...R

I concur.

In fact, "hacking" a Honda or Aldi "inverter" petrol generator might be the most direct approach. Note that these may have a governor system that would adapt to your water flow control as well.

Welcome to the Arduino forum. I am sure you can get an Arduino to do what you propose.

However, this statement bothers me: "Since I want the alternator to produce 120 VAC @ 60 Hz, the alternator's drive shaft must maintain 3600 RPM, regardless of the load place on the alternator's output, to maintain that voltage and frequency.".

That implies a dead short will still produce the required power. Generators are funny machines. When the load is TOO great for the machine to handle, the generator will begin to slip passed the magnetic lines of force and will lead to over speed and self destruction. So you need to also regulate for overspeed.

Another question: Do you actually know the water power source can supply the torque/power to spin the generator at the required load?

Another generation problem is the time lag between knowing the load has increased and the time for the water source to begin to apply more force. Just because you open the gate does not mean the water flow will immediately increase. The entire volume of water in the pipe must also increase flow or you create a vacuum that will be heard as water-hammer.

I have to agree, the best solution is to generate a constant power and us a solid state inverter to give you the AC.

Paul

Hi,
Welcome to the forum.

Do you want to control frequency AND output voltage by modulating the water flow?
If so, it won't work.

Go and have a look at your alternator and see how it works, you do not regulator output voltage by adjusting the rotational speed of the shaft.

Can you tell us your electronics, programming, Arduino, hardware experience?

Tom...

Another issue I foresee , is if the load suddenly switched off you may get over speed and or overvoltage before the control system can compensate .

Having said that the type of alternator , it’s excitation method and the power factor of any load will influence all this . It’s a complex subject . Also be aware of earthing regulations ( you probably can’t use the local power companies Earth ) and or those for paralleling ( if you propose to do that )

Dave-in-nj: I would prefer to use the voltage output of the Alternator instead of the rotational speed, of its shaft, but that is an option and thanks for the suggestion.

Robin2: My electronics skills are too limited for "me" to be able to control frequency via an electronic circuit without using an inverter system. I know it can be done without that type of system, but I don't know how to design it. Thanks for the suggestion.

Paul__B: I plan on using an Alternator head to produce the required output voltage/frequency and load current. The same kind used in those type of units, I think.

This is the "type" of "head" I am considering (This particular unit may not have the correct wattage output that will finally be needed. That will need to be decided on, once the WPM is built and its output potential determined):

Paul_KD7HB: I don't plan on allowing a direct short. (Momma raised ugly kids, not stupid ones. ) So a proper fusing system will need to be built into the overall system to prevent that possibility. Thanks for reminding me to do so.

I am aware of the positive feedback to the motor system that could result in over-speed with a sudden loss of load on the Alternator, I plan on controlling that with a separate hand-adjustable valve, that is preset to not permit a faster "unsafe" drum speed, by limiting/controlling the maximum allowable water flow rate to the drum with that valve.

Once the drum rotates at 60 to 100 RPM it will "draw" its own water supply up to the maximum permitted to it (controlled by its feed-pipe size, the safe-guard valve and the proportional valve settings). My maximum pump flow rate is 40 GPM or approximately 16 fps. How that will translate into drum rotation speed and torque will have to be determined by testing after construction. The water supply line from pump to drum is approximately 3', so the water response time should be fairly short, though definitely not instantaneous.

This unit is to serve as an emergency backup when there is a loss of "mains" power to the home. As such, it is intended to be able to run as much of the house load, at those times, as the unit can provide. (i.e. ideally, HVAC, water heater, some lights and wall outlets, cooktop, microwave, refrigerator, and TV, etc.).

I am building the WPM part now and will determine its maximum available HP output and rotational speed after it is completed and tested. Then I will purchase the Alternator head accordingly. That in turn will determine how much of the normal house load this unit will be able to replace in the event of a "mains" power failure. The WPM should hopefully produce somewhere between 15 to 20 HP output, if it performs as designed.

TomGeorge: I may be wrong, but if I understand what was written about the type of proposed Alternator head, to obtain 110 VAC @ 60 Hz the shaft must rotate at 3600 RPM. (I don't know about Alternator heads, per se, but for most of the generators I have ever heard of, the voltage, frequency and amperage output go up and down as the speed of the Alternator's rotor shaft goes up and down.) Some Alternators I have heard of maintain the same general output voltage and frequency range, with little change, once the rotor rotates above a certain RPM (i.e. a car alternator). I know I could run the output through an inverter/battery system, but I don't want to have to use THAT many batteries or the cost of replacing them every three or four years. Of course, an alternative possibility might be to use an inverter/super-capacitor system instead.

My electronics experience is limited to building already designed circuits from their schematics, not designing them myself. I am brand new to Arduino. I have programmed personal-sized computers, years ago, to some degree, with limited C++ skills. But I have some understanding as to how to write Arduino sketches, but I am still learning.

Hammy: Yes, I am worried about that as well. I may have to find a way to build-in an over-voltage "protection" aspect to my overall control circuit. I hope to be able to control the speed of response in the valve by spending the money needed to get a quick response valve, but the final response time is on my mind as well. As for over-speed, please see comment to Paul_KD7HD above.

There will be a total disconnect from the "mains" when this unit is in operation. And it will have its own breaker box and separate grounding rods, sufficiently far away from that of the "mains". Once the device is operational, I plan on having it installed by a licensed electrician with proper County inspections and approval.

Hopefully, I responded to everyone's concerns and comments.

Some questions to those of you who are suggesting that I use an inverter system:

Am I wrong that an inverter will change its input "draw" current requirements, from its source, based on its output load "draw" current requirement changes?

Can a system, using only a DC to AC inverter and an AC alternator and bridge-rectifier, actually be built such that, as the inverter's output load current needs vary, there will not be a corresponding change needed in the alternator's output that is feeding power to the inverter, to provide a constant voltage and frequency, under those load changes to the inverter; without having to use batteries or super-capacitors to provide the needed varying power to the inverter and using the alternator to recharge those batteries or capacitors as their power is depleted?

Thanks again for all the wonderful input.
Rick

rickinva:
Robin2: My electronics skills are too limited for "me" to be able to control frequency via an electronic circuit without using an inverter system. I know it can be done without that type of system, but I don't know how to design it.

Seems to me you have just talked yourself into using an inverter system

...R

Not if it requires using batteries or capacitors to supply the output voltage and current to run the items during a loss of mains power.

Hi rickinva, apologies if this has been said and I missed it but you control the output voltage of an alternator by controlling the field current. You can't control it by anything to do with the rotational input as your primary aim for this is to keep it at 3600 RPM.

You don't need to control the current as the load does that, you just need to make sure there is overload protection.

It might be the case that the proposed alternator has a control system built in so you don't need to worry about it, certainly looks like it from the photo.

Car alternators are designed to produce DC so their rotational speed can vary widely. They are actually 3 phase alternators with a 3 phase rectifier on the output of the stator. As the output is rectified the frequency does not matter.

Yes, alternators regulate output voltage by controlling the rotor field not the RPM. Don't mix up alternators with generators.

But you intend to not use the rectifier to get AC and maybe more power than the alternator is wired for? Not a good idea.
Get an inverter.

With alternator, more RPM lowers the internal field that lowers resistance to turn, you don't want to turn near stall with a large amount of power made feeding back into the rotor field. If your one generator isn't enough then see about two or lowering your power demand.

rickinva:
Not if it requires using batteries or capacitors to supply the output voltage and current to run the items during a loss of mains power.

Whether it does or not is entirely within you control.

To be honest I don't understand where mains power comes into the picture. I thought your plan was to generate your own power. You can't connect your generator or inverter to the mains without the approval of the electric utility - and that won't be cheap.

...R

Hi,
What is the AC load you will have on the AC generator?

Tom...

Sorry, for the lengthy delay in responding, but Christmas got in the way.

Responding to comments after my last post:

PerryBeddington:

I now understand that the voltage output of my alternator does not get controlled by the speed of the alternator’s shaft but rather by the voltage regulator on the alternator that alters the current to the field coil.

However, isn’t the output current of the alternator controlled by the speed of the alternator’s shaft?

So, for a given momentary shaft rotation speed, as the alternator’s load varies, won’t that affect the output current draw which in turn affects the needed speed of the alternator’s shaft, which in turn will affect the needed speed of the water powered motor which in turn needs to have the water flow rate to the motor’s drum controlled.

Since I plan on using a professionally built portable power generating alternator head, with a hoped for continuous wattage output maximum of 7.2 kW. The system will be restricted to 60 A @ 120 VAC. Thus, with appropriate fuses/breakers, there should not be an overload protection problem.

GoForSmoke:

I honestly do not understand what you are trying to tell me when you said," With alternator, more RPM lowers the internal field that lowers resistance to turn, you don’t want to turn near stall with a large amount of power made feeding back into the rotor field."

Please re-explain what you mean, remembering my limited knowledge in electronics.

As for needing “additional alternators”: Depending on the final output power able to be provided by my water powered motor, I will restrict what is powered by the alternator’s maximum continuous wattage output. If the present WPM proves to be too limited in output power, then a larger more powerful WPM will be built to provide the needed drive power for a larger more powerful alternator head.

Robin2:

If I understand inverters well enough, they are usually used with a more stable/fixed power source, like a battery/battery bank or a capacitor/capacitor bank as the input power and as the inverters output load varies, the input power varies accordingly. I have never heard of using an alternator to directly feed the input power needs of an inverter.

I agree that an inverter system would easily control the frequency and voltage output of the inverter for the load, but if only an alternator is used to power the inverter, then as the load on the inverter varies, so would the alternator’s output to the inverter need to vary and I don’t see an advantage using the inverter, from that aspect.

The inverter option creates some problems not created by using an factory built alternator head. I either have to buy expensive pure sine wave (PSW) inverters to power my non-resistive loads, of which there will be many (i.e. fan motors, microwaves, washing machine, electric clothes dryer motor, TVs, kitchen motor driven appliances, etc.) or I will have to make a much more complicated sine pulse width modulator (SPWM) circuit to change my 5 kW modified sine wave (MSW) inverter’s and my other smaller MSW inverters’ outputs, so they will work (some what more efficiently) in supplying power to my non-resistive loads, along with my PSW 1.6 kW inverter.

But THAT would require an Arduino controller circuit that would put to shame the one that I already need to control the water flow to a proportional valve used to control the water supply to my WPM in my present design, (which I’ll already need help in designing, if that is something an Arduino circuit can provide). Which is the original purpose of this thread to determine if such a circuit can be designed using an Arduino and the best way to do so.

As for connecting to the public utility power grid, THAT is NEVER intended. Yes, I am building an off-grid power unit to be used as a backup for when the power grid goes down in storms or other reasons. The device I am building, I want to power all or some of the home when such power failures occur. At other times, the house will be powered by the grid as it is now.

So, this device will have its own breaker box, totally separate from the grid breaker box. Its gound will be totally isolated from that of the power company’s, so no accidental crossover will occur. Like the grid (150 A) breaker box, it will have an incoming limiting breaker (approx.60 A) and disconnect switch.

When a power failure occurs, the grid disconnect switch will be turned off and the backup breaker box’s disconnect switch will be turned on. All breakers to circuits not being driven by the backup device will be turned off in the “mains” breaker box. The backup system is to be installed by a licensed electrician with all appropriate County permits and inspections. I realize that the electrician will have to install a disconnect system (where both boxes can NOT be turned on at the same time) for safety sake on the grid.

TomGeorge:

The answer to your question can not be given at this time. Until the water powered motor is completed and tested for its maximum output power and shaft rotation speed, a determination as to the size of an alternator head that it can drive will not be known.

It is hoped that as much of circuits that the present grid system powers in the house now, can still be powered by the backup system during a power failure. We are hoping for at least 7.2 kW worth of load.

Of course, not all house loads can be used during the power failure with an approx. 60A supply at the same time, that can be driven by a 150 A supply.

Rick

Hi,
So you are designing a household standby power system, for how long does your mains power drop out?

The amount of power you can get from a water powered alternator depends on the water pressure or head of water.
What is the head of water that you have available?
What is the flow rate of the water supply?

These two parameters you need to find out first before looking at any hardware or control systems.

Tom..

rickinva:
If I understand inverters well enough, they are usually used with a more stable/fixed power source, like a battery/battery bank or a capacitor/capacitor bank as the input power and as the inverters output load varies, the input power varies accordingly. I have never heard of using an alternator to directly feed the input power needs of an inverter.

It would hardly be too difficult to add a battery ?

...R

I now understand that the voltage output of my alternator does not get controlled by the speed of the alternator's shaft but rather by the voltage regulator on the alternator that alters the current to the field coil.

However, isn't the output current of the alternator controlled by the speed of the alternator's shaft?

So, for a given momentary shaft rotation speed, as the alternator's load varies, won't that affect the output current draw which in turn affects the needed speed of the alternator's shaft, which in turn will affect the needed speed of the water powered motor which in turn needs to have the water flow rate to the motor's drum controlled.

Since I plan on using a professionally built portable power generating alternator head, with a hoped for continuous wattage output maximum of 7.2 kW. The system will be restricted to 60 A @ 120 VAC. Thus, with appropriate fuses/breakers, there should not be an overload protection problem.

You ask if the output current is controlled by the speed of the alternator shaft. Two answers and one question:

The question is, why do you think this is the case?

Answer 1, no. The only thing that is controlled by the speed of the alternator shaft is the output frequency. For a 2 pole machine this is 50Hz at 3000RPM or 60Hz at 3600RPM because one revolution of the shaft gives one cycle. For a 4 pole machine it is twice that. You are controlling the speed of the shaft to keep the frequency constant, so even if the speed of the shaft did control the output current it would not be any use for that purpose as the frequency would be all over the place.

Answer 2, no. Do you know Ohm's law? If not please find a tutorial about it as it's essential basics for anything electrical. Ohm's law tells you the relationship between voltage, resistance and current. The alternator has a certain output voltage, which you want to keep constant, the load has a certain resistance. As a result of these 2 things a current will flow in accordance with Ohm's law. The load takes whatever current it needs when you apply the appropriate voltage. The alternator does not control the current, the load does.

Having said that you need the alternator and its control system to limit the current in the event of overload. In order for this to happen, when there is an overload, the alternator will reduce its voltage to lower the current, again in accordance with Ohm's law. As you intend to buy an alternator with a built in control this should all be taken care of for you.

I think I saw in one of your posts that this is a back up system. I have a back up system that consists of a 50v 12Ah battery with a 50v power supply and inverter. Keeps the lights on and me connected to the internet, doesn't power the TV. If I had access to a stream I think I'd be doing what you are doing, sounds so much more fun Please post photos of the finished installation.

PerryBebbington:
I have a back up system that consists of a 50v 12Ah battery with a 50v power supply and inverter. Keeps the lights on and me connected to the internet, doesn't power the TV.

Sounds sensible. The OP should be using his alternator to charge a battery.

...R

Robin2:
Sounds sensible. The OP should be using his alternator to charge a battery.

With an inverter to provide his 60 Hz power.

Either the inverter is in the generator itself, or you have a float charged battery and inverter. Whichever way you look at it, in this day and age the solid state inverter is the answer, And if you want "no break", you have no choice but a battery.